A nonstoichiometric spinel phase (Li1.02Mn1.90Y0.02O4-yF0.08) was synthesized using natural polymer net method. It was characterized by XRD and XPS. The particle size and shape of the expected compounds were observed by Transmission Electron Microscopy technique. The composition of new spinel phase was checked by ICP. The electrochemical properties of the new spinel phase (Li1.02Mn1.90Y0.02O4-yF0.08) were also investigated. The results showed that the Li1.02Mn1.90Y0.02O4-yF0.08 behaved excellent recharge ability to compare with stoichiometric LiMn2O4. The initial discharge capacity of the battery was 128.5 mAh/g when current density was 1 mA·cm-2 over voltage range of 4.4 to 3.0V. The discharge capacity could retain about 96% after 100 cycles when metallic lithium was anode. The outstanding electrochemical properties of Li1.02Mn1.90Y0.02O4-yF0.08 make it possible as a promising cathode material. The novel synthesis method provides a simple and effective route for inorganic material synthesis.